Various aerospace and terrestrial applications require lightweight materials with very high mechanical properties, particularly specific modulus and strength. Carbon nanotubes and graphene sheets have been found to be such materials. In addition, they have been found to have excellent electrical and thermal transport properties. However, translating the excellent properties, particularly mechanical and thermal transport, at the nanoscale level to bulk materials has proven to be a difficult challenge. In order for the nanotubes to be used in applications, they must be spun into yarn(s), sheet(s), and other macroscopic forms introducing relatively weak tube-to-tube and inter-bundle bonds. Also, the nanotubes tend to be entangled, and they therefore do not all contribute in load bearing. Weak coupling at tube and bundle interfaces also leads to mechanical and thermal transport that are much lower than would be expected from the carbon nanotube or graphene properties.